Re: [802.3_100GNGOPTX] Reach on MMF
I believe that if the study group is going to set a reach objective for a 100GBASE-SR4 port type, that it would be highly recommended that we support the same reach as the 40GBASE-SR4. End users that have gone through the effort to install ribbon fiber OM3 or OM4 fiber to support 40G will be much happier with us if we permit them to re-use the same fiber for 100G. Forklift upgrades of equipment and cabling also slows deployment of the technology, so from a broad market potential and economic feasibility standpoint, supporting the same reach as 40G just makes good sense.
As for SMF solutions, it would be good to understand the relative cost difference between a 100G LR4 module that is required to meet the 10 km reach vs one that is shorter. For those that may remember 802.3ae, there was a 2 km SMF reach objective. That was the target reach for campus networks with 10 km and 40 km targeting the MAN. It was discovered that the relative cost difference between 2 km and 10 km was insignificant and that by bundling them into one port type 10GBASE-LR, the task force could increase the market potential for that device.
As we stand today, 802.3ba has a huge reach and cost discrepancy between the 100/150 m MMF solution and the 10 km SMF solution. In my humble opinion, we need to understand the potential impact to the cost (in relative terms) between a solution that can satisfy the campus market vs. the one specified for the MAN. There are some that would also like to use SMF within the data center without the cost burden associated with 100GBASE-LR4. The key will be to understand if there is a breakpoint of reach vs. cost that makes the solution economically viable and has good market potential.
The one other aspect that concerned me during the study group meeting was that in Paul Kolesar's slides there was a diagram of the network architecture. I think that diagram is a bit outdated, but that wasn't the main reason I was concerned. What I noticed was that the connection from the access switches to the servers was labeled "Copper horizontal cabling". Why was that connection being assumed to be copper? The data Paul showed indicated that there was a large number of single reach hops that were under 10 m. Paul also highlighted that there was a trend to longer MMF reach. This makes complete sense if one assumes that data centers are transitioning from centralized switches to end-of-row or top-of-rack switches. Paul's data correlates very well with information that I've received about the movement from centralized to end-of-row (or center-of-row). That being said, maybe there is another cost breakpoint for shorter MMF links, say 15-20 m. That to me would be interesting !
data to have for comparison and objective setting.
Thanks,
Brad
-----Original Message-----
From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
Sent: Monday, October 10, 2011 12:32 PM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: [802.3_100GNGOPTX] Reach on MMF
Hi
It great to get some end users feedback on MMF reach, as you know 40Gbase-SR4 has reach of
-100 m on OM3
- 150 m on OM4
Single mode PMD is also with in the scope of 100GNGOPTX study group, when the days come that single mode PMDs are low cost, power, and size then I expect MMF ribbon reach could get limited to 10's meters. I have my finger crossed for that day!
Now with reality and unknown in front of us if the ultimate PMD could be developed, what should the reach of
100Gbase-SR4 be?
Historically single mode PMDs have been larger, higher power, and higher cost. For example 100GBase-SR10
is supported in the CXP form factor and 100Gbase-LR4 is supported in the CFP form factor, the CFI presentation slide 11 http://www.ieee802.org/3/100GNGOPTX/public/jul11/CFI_01_0711.pdf
shows 32 ports of CXP and only 4 ports of CFP! So for some period of time we could find ourself that the MMF PMD is the only option on the highest density platform. This is why we need to carefully study this subject specially with in the context of larger data centers see slide 7 http://www.ieee802.org/3/100GNGOPTX/public/sept11/ghiasi_01_a_0911_NG100GOPTX.pdf
Thanks,
Ali